ESTRO 2023 - Abstract Book

S309

Sunday 14 May 2023

ESTRO 2023

where h is the time in hour and (e_i ) are the standard unit vectors in 24th dimension. This formulation was derived to ensure that for all n ∈ {1,2,3,…,11}, the distance ǁ (T_(h+n))-(T_h) ǁ in Euclidean 24-space increases as n increases but remains the same for all h ∈ {0,1,2,…,23}. We subsequently performed dimension reduction analyses of biometric data using uniform manifold approximation and projection (UMAP) and principal component analysis (PCA). Results PCA and k-means clustering revealed 5 clusters of activity profiles, one of which was associated with low physical activity, high metabolic rates, and higher chance of death and cancer progression. Multivariate logistic regression showed that 7- day maximum total steps, minimum sedentary minutes, maximum lightly active distance, and maximum very active distance were independently associated with lower likelihood of progression in 2 months (p<0.0001). Similarly, maximum total steps and total daily distance predicted lower likelihood of death in 1 year (p<0.0001). The multivariate model had specificity and sensitivity of 100% and 94%, respectively, for predicting progression and specificity and sensitivity of 98% and 85% for predicting death in 1 year. Unsupervised dimension reduction revealed a circular cluster consisting of 24 temporally ordered subclusters containing hour-to-hour biometric data (Figure 1). Activity level was highest in the center but lower in the periphery and lowest in subclusters outside the circular cluster. At the same time, clusters associated with low physical activity level were associated with patient death and with cancer progression (Figure 2).

Conclusion In this study, we demonstrated that multivariate continuous biometric recording can be used to predict survival and progression in metastatic head and neck cancer. We are also the first to employ unsupervised dimension reduction of biometric data to assess alterations in the circadian rhythm as a tool detect disease progression.

Poster Discussion: Clinical Brachytherapy

PD-0407 HDR brachytherapy for Cervical Cancer: Evolving anaesthetic technique to improve patient experience D. gregory 1 , T. Christmas 2 , S. Prewett 1 , K. Bradshaw 1 , J. Latimer 3 , S. Duke 1 , L.T. Tan 1 1 Cambridge University Hospitals, Clinical Oncology, cambridge, United Kingdom; 2 Cambridge University Hospitals, Anaesthesia, cambridge, United Kingdom; 3 Cambridge University Hospitals, Gynaecology, cambridge, United Kingdom Purpose or Objective The use of intra-cavity applicators, particularly interstitial implants to deliver HDR brachytherapy for cervical cancer is consistently associated with high levels of pain. 41% of patients experience PTSD at 3 months. In our institution BT is delivered with one applicator insertion, with 3 or 4 fractions delivered over 3 days. Typically insertions were under GA with epidural in the post operative period. We noted that under continuous epidural analgesia pain scores for women were high whilst the applicator remained in situ and numerous pain interventions were required. Following the appointment of a regular brachytherapy anaesthetist we changed practice to a combined spinal-epidural with intrathecal diamorphine to provide anaesthesia for insertion and post-insertion analgesia with epidural analgesia. A retrospective review of cases over a 5 year period evaluated the impact of this intervention.